Extendable/retractable support column

ABSTRACT

An extendable and retractable column which is formed from at least three linked sections. The linked sections include a plurality of individual sections linked end to end. As the linked sections are extended, each of the individual sections engage adjacent individual sections to form a column. As the linked sections are retracted, each of the individual sections disengage from the adjacent individual sections and the column may be retracted for compact storage. Methods of forming such an expandable/retractable column are also presented.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/023,158, filed Jun. 29, 2018, which is a continuation of U.S. patentapplication Ser. No. Ser. No. 15/650,065, filed Jul. 14, 2017, now U.S.Pat. No. 10,012,344, issued Jul. 3, 2018, which is a continuation ofU.S. patent application Ser. No. 14/607,524, filed Jan. 28, 2015, nowU.S. Pat. No. 9,709,212, issued Jul. 18, 2017, which is a continuationof U.S. patent application Ser. No. 13/758,482, filed Feb. 4, 2013, nowU.S. Pat. No. 8,955,811, issued Feb. 17, 2015, which is a continuationof U.S. patent application Ser. No. 12/537,948, filed Aug. 7, 2009, nowU.S. Pat. No. 8,366,066, issued Feb. 5, 2013, which is a continuation ofU.S. patent application Ser. No. 12/033,225, filed Feb. 19, 2008,Abandoned, which is a continuation of U.S. patent application Ser. No.10/826,867, filed Apr. 16, 2004, now U.S. Pat. No. 7,357,365, issuedApr. 15, 2008, which claimed benefit under 35 U.S.C. 119(e) of U.S.provisional application Ser. No. 60/463,480, filed Apr. 17, 2003, all ofwhich are incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to a support column and morespecifically to an improved extendable/retractable column for use insupporting elevated structures that can be extended from a portable orfixed platform or other substrate.

DESCRIPTION OF THE PRIOR ART

Structures that comprise one or more elements that can be linkedtogether to form a rigid column or other structure are well known in theart. Structures of this kind may be used to form an elevated orelevatable platform to elevate a person or equipment or to support otherstructures relative to a supporting substrate or platform. See U.S. Pat.Nos. 2,661,082; 3,397,546; 4,024,595; 4,089,147; 4,237,662; 4,920,710and 6,112,474.

Extendable/retractable towers (or simply “retractable towers” as theymay be referred to herein) of this kind may be further utilized asportable telecommunications towers where various sites can be testedwithout constructing a costly, permanent test tower. Retractable towersmay also be used as supports for temporary lighting systems for sportingevents, emergencies, on ships or the like. In general, retractablecolumns or towers may be used for any application where it is desired toprovide a support for a person or equipment at an elevated locationrelative to a reference platform or substrate.

Retractable towers or columns of the general type to which the presentinvention relates are shown and described in U.S. Pat. Nos. 4,920,710and 6,112,474. In general, these patents disclose a retractable columnformed from three link chains or three flexible webs. These chains orwebs are linked with one another as they are vertically extended to forma tower with a generally triangular cross-section. In these patents, thethree link chains or three flexible webs are each stored on a rotatabletake-up mechanism located at or near the level of the platform or othersupporting substrate. During operation, each of these three link chainsor flexible webs is centrally directed so that the link chains and theflexible webs are connected with one another and driven vertically.Accordingly, each of the retractable columns in these patents alsoincludes means for interconnecting the three link chains or flexiblewebs together and means for driving those elements vertically upwardly.

In U.S. Pat. No. 4,920,710, the interconnection means includes theprovision of hook members extending laterally outwardly from corners ofeach chain member for interconnection with corresponding outwardlyextending hook members of an adjacent chain member. In U.S. Pat. No.6,112,474, this interconnection means is in the form of a set of teethlocated along opposite edges of the webs with each of the teeth having aneck and a crown region larger than the neck.

The drive mechanism in U.S. Pat. No. 4,920,710 includes a plurality ofrotatable tooth gears positioned within the triangular column whichengage corresponding toothed racks on at least two of the chain members.These toothed gears are rotatable about a horizontal axis. In U.S. Pat.No. 6,112,474, the drive means includes a drive roller associated witheach of the flexible webs. Each of these drive rollers is rotatableabout a horizontal axis and is located outside the generally triangularcolumn. Each roller engages a series of spaced openings in each of thecontinuous webs.

Although prior retractable columns have been satisfactory for someapplications, significant limitations exist due to the nature of thedrive mechanisms, the means for providing stability to the column duringand after erection, the means for vertically supporting the columns andthe complexity of the structures, among others. Accordingly, there is aneed in the art for an improved extendable and retractable tower orcolumn structure that overcomes these limitations.

SUMMARY

The present invention relates to an extendable/retractable columnincluding at least three linked sections, each linked section includinga plurality of individual sections pivotally connected to one another inend-to-end relationship, and each linked section positioned adjacent toat least two other linked sections. Each individual section includes aninner surface, a first end and a second end and a connection tab at thefirst end of the individual section. The connection tab extends inwardlyof the inner surface of the individual section. Each individual sectionalso includes a tab receiving surface at the second end of theindividual section. The tab receiving surface engages the connection tabof an individual section of one of the adjacent linked sections.

The present invention further relates to an extendable/retractablecolumn including a plurality of linked sections and a plurality of driveslots in at least one of said linked sections. The column also includesa linear drive member rotatable about an axis generally parallel to thecolumn. The linear drive member includes a power screw configured toengage the drive slots. Rotation of the power screw of the linear drivemember extends or retracts at least one of the linked sections and theplurality of linked sections engage each other to form the column as thelinked sections are extended. The plurality of linked sections disengagefrom each other as the linked sections are retracted.

The present invention also relates to an extendable/retractable columnincluding a plurality of linked sections each comprised of a pluralityof individual sections pivotally connected to one another in end-to-endrelationship. Each of the individual sections includes a first andsecond end and a pair of opposing sides. Each individual sectionincludes a plurality of projections extending outwardly from each of itssides. The projections of a first individual section of a first linkedsection engage the projections of a second individual section of asecond linked section when the first and second linked sections areinterconnected with one another to form the column.

The present invention relates still further to an extendable/retractablecolumn including a plurality of linked sections each comprised of aplurality of individual sections pivotally connected to one another inend-to-end relationship. Each individual section is a one-piece integralstructural unit.

These and other features and objects of the present invention will bemore fully described below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the description, illustrate several aspects of the invention andtogether with the detailed description, serve to explain the principlesof the invention. A brief description of the drawings is as follows:

FIG. 1 is an isometric view of the base of the retractable column of thepresent invention showing the linked sections in their fully retractedform.

FIG. 1a is an elevational top view showing the springs for biasing thebale of wound linked sections inwardly.

FIG. 2 is an isometric view of a portion of the linear drive mechanismusable in the present invention.

FIG. 3 is an isometric view of the base of the structure of the presentinvention with the drive mechanism and the three linked sectionsremoved.

FIG. 4 is an isometric view of the outer stabilizing or constrainingring.

FIG. 5 is an isometric view showing the upper portion of the outer ringassembly and the drive mechanism.

FIG. 6 is a view, partially in section, showing the relationship betweenthe drive mechanism, a portion of the outer ring assembly and the linkedsections as the linked sections are being driven.

FIG. 7 is a side elevational, schematic illustration showing the mannerin which the linked sections are centrally fed and vertically driven.

FIG. 8 is an isometric view of one of the individual sections as viewedfrom the lower, outer corner.

FIG. 9 is an isometric view of one of the individual sections as viewedfrom the lower, inner corner.

FIG. 10 is an elevational view as viewed from the outer side of anindividual section.

FIG. 11 is an elevational view as viewed from the inner side of anindividual section.

FIG. 12 is an isometric view showing a pair of sections verticallylinked together.

FIG. 13 is an isometric view showing a plurality of the linked sectionsinterconnected to form a partial column.

FIG. 14 is an isometric view showing the details of the interconnectionbetween laterally adjacent sections, with the pivot rod removed.

FIG. 15 is an isometric view showing the details of the positionedrelationship between the shear tabs of laterally adjacent sections.

FIG. 16 is a view, partially in section, as viewed along the sectionline 16-16 of FIG. 10.

FIG. 17 is an enlarged, fragmentary view of one of the pivot supporttabs showing the upwardly extending connection member.

FIG. 18 is a view, partially in section, as viewed along the sectionline 18-18 of FIG. 17.

FIG. 19 is an enlarged, fragmentary view showing the connection betweenthe connecting tab on one section with the receiving recess on avertically adjacent section of an adjacent linked section.

FIG. 20 is a top view of a central portion of an alternative embodimentof an extendable/retractable column according to the present invention,having a central power screw for extending and retracting the tower.

FIG. 21A is a side view of the power screw of FIG. 20, along with aninfinite length power nut made of a plurality of lugs, with the lugsengaging openings in an inner face of a section forming a portion of theextendable/retractable column.

FIG. 21B is a top view of the power screw and power nut of FIG. 21A,with the lugs of the power nut engaging the inner faces of a pair ofsections forming a portion of the extendable/retractable column.

FIG. 22A is a side view of one of the lugs forming the infinite lengthpower nut of FIG. 21A.

FIG. 22B is a view of the power screw engaging portion of the lug ofFIG. 22A.

FIG. 22C is a bottom view of the lug of FIG. 22A.

DESCRIPTION OF THE PREFERRED EMBODIMENT AND METHOD

Reference will now be made in detail to exemplary aspects of the presentinvention which are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

The present invention relates to an extendable/retractable supportcolumn or tower and method for forming the same. The support column inaccordance with the present invention is of the type which includesthree or more (but preferably three) linked sections which are stored inwrapped form on a rotatable take-up or delivery mechanism at the base ofthe structure. In this type of extendable/retractable column, each ofthe linked sections is fed centrally where it engages and isinterconnected with an adjacent linked section. These interconnectedlinked sections are then driven vertically upwardly to extend the columnor driven vertically downwardly to retract the column. When the columnis erected, the three interconnected linked sections form a columnhaving a triangular cross-sectional configuration.

In the present invention, each of the linked sections is comprised of aplurality of individual sections which are linked together, or pivotallyconnected with one another, in end-to-end relationship. Throughout theapplication, various directional and positional references will be usedsuch as upper, lower, inner, outer, etc. When used, these will generallyrefer to orientation of the individual sections or the linked sectionsin their position within an erected column. For example, the “upper”direction will be the direction toward the upper end of an erectedcolumn, while the “lower” direction will be the direction toward thelower end of an erected column. Similarly, the “inner” direction will bethe direction which faces inwardly within the column, while thedirection “outwardly” will be the direction which faces outwardly fromthe column.

With the above general description of the extendable/retractable columnof the present invention, the detailed and preferred structure isdescribed with reference to the drawings. With reference first to FIGS.1 and 3, the column includes a base 10 and three take-up and deliverysupport frames. Each of these support frames is comprised of a pair oflaterally spaced, substantially parallel, frame members 11 and 12. Eachof the frame members 11 and 12 includes a base flange 14 for connectionto the base 10 and a top flange 15 to rotatably support a take-up anddelivery mechanism shaft 17 (FIG. 1). As shown, the three support framesare equally circumferentially spaced relative to the center of the base10 and each of the top flanges 15 slopes downwardly toward the center ofthe base 10.

As shown best in FIG. 1, each of the take-up and delivery support framessupports a linked section 16 a, 16 b and 16 c. Each of these linkedsections 16 a-c is wound or wrapped around a center shaft 17 and acenter support 13. The ends of the shaft 17 are rollingly supported bythe upper flanges 15. As the individual sections from the linkedsections 16 a, 16 b and 16 c are fed from their respective take-upmechanisms, the shafts 17 roll down the inclined flange 15 toward thecenter. Accordingly, the weight of the rolled up linked sections 16 a-cexerts a component inward force on the shaft 17, thereby biasing theentire rolled up bundle or bale of linked sections toward the center Ifneeded or desired, additional bias forces can be applied to the shaft 17through the utilization of various types of spring members includingcoil springs, torsion springs and the like to bias the shaft 17 and thusthe entire bale of linked sections 16 a-c toward the center. FIG. 1ashows a coil spring 23 pulling or biasing the bale of linked sections 16a-c toward the center. The spring 23 has one end connected with theshaft 17 and the other end connected with a portion of the rollersupport frame near its inner end.

With general reference to FIG. 1 and more specific reference to FIG. 2,a linear drive mechanism is mounted to the base 10 at the center of thebase and take-up and delivery mechanisms. The drive mechanism, which isbest shown in FIG. 2, includes three linear drive members 18. Whenassembled and connected with the base 10, the drive members 18 arerotatable about an axis which is generally parallel to the erectedtower. Each member 18 includes a continuous spiral or helical drive rib21 extending throughout its length. Each drive member 18 also includesan upper axial shaft portion 19 and a lower axial shaft portion 20.These shaft portions 19 and 20 rotatably mount the drive mechanisms 18within the triangular mounting blocks 22 and 24. A further pair oftriangular mounting blocks 25,25 are spaced from the lower mountingblock 24 and include openings through which a drive shaft can extend torotate or drive the lower shaft portions 20 and thus the linear drives18. Such a drive shaft (not shown) extends upwardly through the shaftopenings 28 in the blocks 25 to drive the shafts 20. The other ends ofthe drive shafts in turn extend through holes 33 (FIG. 3) in the floorof the base where they are connected to the output shaft of a drivemotor 27 (FIGS. 1 and 3). The drive shafts extending through the floorof the base are connected to the motor output shaft by a chain andplurality of gears. These may be mounted within the base 10.

Preferably, each of the triangular mounting blocks 22, 24 and 25 isprovided with a stabilizing notch on each of its sides to receive astabilizing or spacing bar 29. In the preferred embodiment, the bars 29are then connected to each of the blocks 22, 24 and 25 by countersunkscrews or the like and the lower ends of each of the bars 29 (the endsopposite the linear drives 18) are connected to the base 10 via aplurality of threaded connectors or other means. In the preferredembodiment, a top triangular mount 30 (FIGS. 1 and 5) is provided at theupper end of the bars 29 and is connected to the bars by set screws.

With continuing reference to FIG. 3, as well as detailed reference toFIG. 4, the structure of the present invention is provided with an outerretaining or constraining ring assembly which is partially shown in FIG.3 and more completely shown in FIGS. 4 and 5. The outer ring assemblyincludes three roller support members 31 and three pairs of bracemembers 32,32. An upper brace member 32 is connected with adjacentroller supports 31 near the upper end of the supports 31, while a lowerbrace member 32 interconnects adjacent roller supports 31 near the lowerend of the supports 31. The brace members 32 interconnect the threeroller supports 31 into a rigid structure having a generally openinterior.

Each of the roller supports 31 includes an outer, planar surface which,when the outer ring is installed, extends in an axial directiongenerally parallel to the erected column. An upper flange 35 and a lowerflange 36 extend radially inwardly from the upper and lower edges,respectively, of the outer wall 34. Each of these flanges 35 and 36 isprovided with a generally circular opening to receive a support post 38(FIGS. 1 and 3). Specifically, each of the support posts 38 extendsupwardly through the opening 39 in a corresponding lower flange 36 andis secured to the corresponding upper flange 35 by a threaded member 40(FIGS. 3 and 5) or other similar means.

With continuing reference to FIGS. 3, 4 and 5, a pair of side flanges 41extend outwardly from the side edges of each of the outer walls 34.These side flanges 41 form or are joined with a pair of spaced rollersupport flanges 42,42 to rotatably support a plurality of rollers 44. Inthe preferred embodiment, each of the rollers 44 is rotatably supportedon a pin or other shaft member extending between the roller supportmembers 42, 42. As shown, each of the pair of flanges 42,42 rotatablysupports three rollers. Thus, when assembled as shown in FIG. 4, thethree roller support members 31 support a total of eighteen rollers. Aswill be described in greater detail below, this outer ring structure andthe plurality of rollers 44 function to constrain and guide the movementof the interconnected column as it is driven upwardly.

Because the outer ring shown in FIG. 4 is supported on the ends of theelongated posts 38, the outer ring “floats” to some extent. In otherwords, it is capable of minimal movement to accommodate small movementsof the column as it is driven vertically.

Having described the take-up and delivery mechanism, the internal drivemechanism and the outer ring assembly, the linked sections 16 a, 16 band 16 c, and in particular the individual sections which are verticallyconnected to one another and make up the linked sections will bedescribed in detail. In describing the individual sections, generalreference is made to FIGS. 8, 9, 10 and 11. Each of the individualsections 45 includes a center section shown by the general referencecharacter 46. The center section 46 includes an outer surface 48 shownin FIGS. 8 and 10 and an inner surface 49 shown in FIGS. 9 and 11. Thecenter section 46 includes a lower edge 54, an upper edge 55, a pair ofside edges 64 and 68, a center opening 50 and a set or series of lineardrive openings or slots 51 and 52 positioned laterally on each side ofthe center opening 50. As shown, each of the openings in the sets 51 and52 is sloped relative to the side edges and general vertical orientationof the center section 46. The sets 51 and 52 comprise a plurality ofspaced, substantially parallel openings extending from the bottom edge54 to the top edge 55. The dimensions and the slope of the openings 51and 52 are designed to accommodate the dimensions and slope or pitch ofthe spiral drive rib of the linear drive 18 shown in FIG. 2. Thus, thewidth of the openings 51 and 52 as measured in the vertical direction(from the edge 54 to the edge 55) approximates or is slightly largerthan the thickness of the drive rib 21 on the linear drive 18 and thedistance between the openings 51 and 52 approximates or is slightlysmaller than the distance between the spiral rib 21. Similarly, theslope of the individual openings 51 and 52 approximates the pitch of thedrive rib 21.

With this structure, the drive rib 21 of each of the linear drives 18engages the drive openings 51 and 52 to drive the interconnected linkedsections vertically. This is shown best in FIG. 6. As shown, thesections of each of the linked sections 16 a, 16 b, 16 c areinterconnected to form a column with a generally triangular crosssection. When the interconnected linked sections 16 a, 16 b and 16 c arepositioned within the area of the linear drives 18 as shown in FIG. 6,the continuous spiral drive rib 21 of each of the linear drives 18extends through a plurality of the openings 51 and 52 to drive theassembled column vertically. As shown, the drive rib 21 of each of thelinear drives 18 engages the openings 51 and 52 of laterally adjacentsections. Thus, each linear drive 18 will engage the drive openings 51of one section as well as the drive openings 52 of a laterally adjacentsection. When the drives 18 are rotated in one direction, the columnwill be extended, while rotation of the drives 18 in the oppositedirection will cause the column to retract. To facilitate this drivemechanism, the openings 51 must be equally spaced from one another inthe vertical direction and the openings 51 in vertically adjacentsections must be spaced from one another so that such equal spacing iscontinued. The same is true for the openings 52. A feature of the driveof the present invention is that the drive member is rotatable about anaxis generally parallel to the axis of the column and that a singledrive member is capable of driving laterally adjacent sections of a pairof linked sections.

A first flange 56 extends outwardly at substantially right angles fromone side edge of the center portion 46 and a second flange 58 extendsoutwardly at substantially right angles from the opposite side edge ofthe central portion 46. The side flange 56 includes an upper pivotsupport tab 59 and a lower pivot support tab 60. Each of the tabs 59 and60 includes a pivot opening 61 and 63, respectively. The outermost edgeof the side flange 56 is provided with a laterally extending rollerguide or engagement flange 62. As shown, the roller engagement flange 62extends laterally toward the flange 58 at approximately right anglesfrom the side flange 56 and substantially parallel to the center section46.

Similar to the side flange 56, the side flange 58 includes an upperpivot support tab 59 and a lower pivot support tab 60. Each of thesetabs 59 and 60 is provided with a pivot opening 61 and 63, respectively.The outermost edge of the side flange 58 is also provided with alaterally extending roller guide flange 62 which extends laterallytoward the flange 56 at approximately right angles from the side flange58 and substantially parallel to the center section 46.

As shown best in FIG. 6, the roller guide flanges 62,62 of the sideflanges 56 and 58 are engaged by the plurality of rollers 44 as thelinked sections 16 a, 16 b and 16 c are driven vertically upwardly orretracted downwardly. As shown in FIG. 6, one of the sets of rollers 44of each of the roller supports 31 engages the roller guide flange 62 ofone of the sections, while the other set of rollers of such rollersupport engages the roller guide flange 62 of a laterally adjacentsection.

Each of the side edges 64 and 68 of the center section 46 is providedwith a plurality of vertical support members in the form of shear tabsor shear members. Specifically, the side edge 64 is provided with aplurality of laterally extending shear tabs 65. These shear tabs 65 arevertically spaced along the side edge 64 and are provided with openings66 between them. The opposite side edge 68 is also provided with aplurality of shear tabs 69. These tabs 69 are also vertically spacedalong the side edge 68. In the preferred embodiment, the dimension ofthe tabs 69 as measured in the vertical direction approximates thedimension of the openings 66 as measured in the vertical direction.Further, the vertical position of each of the tabs 69 along the sideedge 68 substantially matches the vertical position of a correspondingopening 66 along the side edge 64. Thus, when the column is assembledwith adjacent linked sections engaged with one another, the tabs 65 and69 will mesh with one another as shown best in FIG. 15 to providevertical support for the individual sections and to distribute thevertical load.

Although the preferred embodiment shows four tabs 65 on the side edge 64and two tabs 69 on the opposite side edge 68, any number of cooperatingtabs may be provided as long as the tabs on the respective side edges 64and 68 are positioned so that they have engaging edges. Such engagingedges assist in vertically supporting the column and the load on thecolumn. These shear tabs also function to better distribute the verticalload on the individual sections along the length of the side edges 64and 68, between the upper and lower edges 54 and 55. In general, severalcooperating tabs with engaging surfaces will better distribute the loadvertically than a single pair of cooperating tabs with engagingsurfaces. Further, although the preferred embodiment shows the loaddistribution elements as a plurality of shear tabs, these distributionelements can take the form of alternate structures such as cooperatingpins or other projections along the side edges of the individualsections which have cooperating or engaging surfaces.

Each of the individual sections 45 also includes a section retaining tab70. As shown best in FIGS. 8 and 16, the tab 70 extends outwardly from aportion of the upper edge 55 of the center section 46 and includes anouter, distal end 71 which is bent upwardly. This retaining tab issometimes referred to as a retaining bill or a “duck bill” and functionsto keep the rolled bales of linked sections 16 a, 16 b and 16 c togetherduring storage and during extension and retraction of the column toprevent the same from unwrapping or unwinding. As shown best in FIG. 16,the tab 70 extends outwardly at about right angles from the upper edge55 of the central portion 46 at a point just below the openings 61. Thisenables the distal end 71 of the tab 70 to engage the pivot rod 72 (FIG.12) of a corresponding section 45 to retain the linked sections in awound condition within the bale.

Each of the three linked sections is formed by pivotally connecting aplurality of individual sections 45 in end-to-end relationship in avertical direction. As shown best in FIG. 12, this is accomplished by apivot rod 72 which extends through the pivot openings 61 at the upperend of one section 45 and through the pivot openings 63 at the lower endof a vertically adjacent section 45. The pivot rod 72 is retained withinthe pivot openings 61 and 63 via cotter pins or other retaining members74 at each end of the rod 72. Although FIG. 12 shows two individualsections 45 pivotally connected to one another by the rod 72, eachlinked section is comprised of a relatively large number of individualsections 45 each pivotally connected to a vertically adjacent section.In the preferred embodiment, a typical column with the ability of beingraised to a height of 20-80 feet or more may have as many as 10-60 ormore individual sections 45 pivotally connected to one another in thevertical direction. When these individual sections are pivotallyconnected with one another to form a linked section, the linked sectionsare capable of being wound into the form of a bale as shown in FIGS. 1and 7. The bale is rotatably supported on the shaft 17. Although thepreferred embodiment shows the rods 72 spanning the entire width of thesections 45 as providing the pivotal connection, separate pivotalconnections such as rivets or the like could be provided at each corner.

With reference to FIGS. 9, 11, 12, 17 and 18, each of the individualsections 45 includes a hook portion or connecting tab 75 which extendsupwardly from an inner portion of the pivot support tab 59 connectedwith the side flange 58. Thus, in the preferred embodiment, the hook orconnecting tab 75 is located at the top of each of the individualsections 45 and extends upwardly for engagement with an individualsection in an adjacent linked section. As shown best in FIGS. 17 and 18,the connecting tab extends upwardly from a portion of the inner edge ofthe pivot support tab 59 and includes a beveled or lead-in surface 76.As shown in FIG. 18, the tab 75 is bent or beveled laterally outwardlyfrom the plane of the pivot support tab 59. This enables the connectingtab 75 to engage and interconnect with a corresponding section in anadjacent linked section.

Each of the individual sections 45 also includes a connection tabreceiving recess 78 formed at the laterally outer, lower edge of thecentral portion 46 and adjacent to the pivot support tabs 60 at thelower ends of each of the individual sections 45. As shown best in FIGS.8 and 9, these recesses 78 extend upwardly to a point generally in thearea of the pivot openings 63 in the tabs 60. During erection of thecolumn, these recesses receive a connection tab 75 from a correspondingsection to connect adjacent linked sections to one another as the columnis erected.

As shown, the tab 75 extends inwardly relative to the inner surface 49of the center section 46 and extends upwardly relative to the upper edge55 of the section 45. Although the preferred embodiment shows the tabs75 located at the upper end and extending upwardly in the recesses 78located at the lower end, these could be reversed, with the tab 75located at the lower end and extending downwardly and the recesses 78located at the upper end. In any event, the tab 75 must be of sufficientlength so that when the linked sections are erected into a column, itengages an inner surface portion of a corresponding section in alaterally adjacent linked section. With this structure, theinterconnection between adjacent linked sections is located on theinside of the erected column. In the present invention, the tabsfunction to retain the plurality (three) of linked sections laterally,while the shear tabs 65 and 69 function to provide the vertical supportand load distribution for the column.

Having described the structural details of the column of the presentinvention, its operation can be understood best as follows. First, threeelongated linked sections are constructed from a plurality of theindividual sections 45 such as those shown in FIGS. 8-11. Theseindividual sections are pivotally linked together by the pivot rods 72extending through the pivot openings 61 and 63 in the tabs 59 and 60 toform the linked sections 16 a-c. Two sections 45 linked together areshown in FIG. 12. The number of sections in any one linked section willdetermine the maximum height to which the column can be extended. Ingeneral, as many as 10-60 or more sections 45 can be pivotally linkedtogether to form an individual linked section.

Each linked section 16 a-c is then wound onto a bale such as that shownin FIGS. 1 and 7. Each of these bales is rollingly supported on a shaft17 which rolls against the upper flange surface 15 of the frame members11 and 12. When in their wrapped or wound position as shown in FIGS. 1and 7, the retaining tabs 70 engage the pivot rod 72 of an associatedsection 45 to keep the linked section retained in a wound condition.

To erect the column, the sections 45 from each of the linked sections 16a-c are simultaneously fed inwardly from the bales toward the center andthen upwardly to erect the column. This is accomplished by engagementbetween the linear drive members 18 and the plurality of drive slots 51and 52 as described above.

As the individual sections 45 of the linked sections 16 a-c are fed intothe central area, the connection tabs 75 of one section slip into thereceiving recesses 78 of a vertically higher section in an adjacentlinked section. This retains the linked sections 16 a-c in a generallytriangular configuration. At the same time, the shear tabs 65 and 69become meshed with one another to provide and distribute vertical loadsupport. Accordingly, the retaining tabs 75 connect the linked sectionstogether into the form of a column of generally triangular cross-sectionand the meshing of the shear tabs or shear members 65 and 69 bear themajority of the vertical load.

An alternative embodiment of an extendable and retractable column 100 isillustrated in FIGS. 21 to 23C, including an alternative drive with apower screw 18 centrally located as shown in FIG. 20. Column 100 usesonly one power screw 18 versus three power screws 18 as shown in FIG. 6.Column 100 includes three power screw nuts, or linked lug sections 85which engage both sections 16 a, 16 b and 16 c, as well as power screw18. These linked lug sections 85 are drawn in a circular fashion(clockwise or counterclockwise) around a path 102 defined about a pulleysystem 86, by the rotation of power screw 18. As each of the linked lugsections 85 are continuous, each of the linked lug sections defines aninfinite length power nut for transferring movement of power screw 18 tothe panel sections 16 a, 16 b and 16 c. In the earlier describedembodiment, as shown in FIG. 6, the power nuts 51 and 52 were located inthe panel sections, items 16 a, 16 b, and 16 c, and each power nut 51and 52 defines a finite length.

The drive approach depicted in FIGS. 20, 21A and 21B relies on a uniquelug 88, shown in FIG. 22. A plurality of lugs 88 may be linked togetherto form a linked lug section 85, and each lug 88 forms a portion of theinfinite length power nut. Each lug 88 may include a portion 89corresponding to the power screw thread 21 (shown in FIGS. 20, 21A and21B), a pair of lifting pegs 90, and a guide rail 91. Portion 89 matchesthread 21 on power screw 18, to transfer motion and force to the liftingpegs 90. The guide rail 91 on each lug 88 keeps the linked lug sections85, in the prescribed path 102 and correctly oriented to engage panelsections 16 a, 16 b and 16 c.

FIGS. 21A and 21B depict one of the three linked lug sections 85, beingdriven by power screw 18. As linked lug section 85 rotates along path102 around pulley system 86, it makes contact in a plurality of slots oropenings 87, which is located in the adjacent panel sections 16 a and 16b, to raise or lower the linked panel sections which make up column 100.Each opening 87 in the panel sections 16 a defines a length L orientedgenerally perpendicular to a direction of extension or retraction 108,which is also the direction of movement of linked lug section 85. Eachopening 87 further defines a width W generally parallel to direction108. Opening 87 includes a end portion 104 with a greater widthpositioned away from a nearest adjacent edge 110 of panel 16 a, and anend portion 106 with a narrower width positioned toward edge 110. Theshape of opening 87 facilitates the entry and exit of a lifting peg 90into and out of opening 87 as a lug 88 of linked lug section 85 rotatesthrough one of a pair of angled portions 112 of path 102. Lifting peg 90would enter or exit opening 87 through wider end portion 104 andtransition into narrower end portion 106 to engage and lift or lowerpanel 16 a. The shape of opening 87 facilitates the movement of liftingpeg 90 into and out of opening 87 while helping preserve the timing oflift of adjacent panels 16 a, 16 b and 16 c so that tabs 65 and 69 alongthe edges of the panels properly engage and disengage to form column100.

While panel sections 16 may vary in width as required for particularapplications, at greater widths, it may be desirable to increase thestrength or rigidity of each panel 16 to improve the overall strengthand rigidity of the tower. External and internal bracing of the tower isnot practical due to the retractable nature of the column. Thus, eachpanel 16 may be include a second component, such as an outer surface 92,as shown in FIGS. 20, 21A and 21B. As shown in these Figures, panelsections 16 a, 16 b, and 16 c, are double walled, having inner surface49 and outer surface 92. The additional outer surface 92 may be attachedby various fastening techniques such as welding, riveting, screwing,etc. This additional outer surface 92 increases the structural inertiato stiffen the panel when appropriate.

Although the description of the preferred embodiment has been quitespecific, it is contemplated that various modifications could be madewithout deviating from the spirit of the present invention. Accordingly,the scope of the invention is intended to be dictated by the appendedclaims rather than by the description of the preferred embodiment.

The following is claimed:
 1. A method of forming anextendable/retractable tower comprising the steps of: providing threelinked sections and a drive mechanism, each linked section including aplurality of pivotally connected vertically adjacent individualsections, each individual section having a first end, a second end, afirst side and a second side, each individual section of each linkedsection being pivotally connected in an end-to-end relationship withrespect to each vertically adjacent individual section, each individualsection having a series of drive openings, a connection tab proximatethe first end and a tab receiving recess proximate the second end; thedrive mechanism including a power screw; wherein the drive mechanism canengage drive openings in individual sections of each of the three linkedsections when the power screw rotates, so that connection tabs ofindividual sections of each of the three linked sections can engage tabreceiving recesses of individual sections in laterally adjacent linkedsections so as to connect such individual sections and connect therespective laterally adjacent linked sections; and rotating the powerscrew in a first direction so that the drive mechanism engages driveopenings in individual sections so that the connection tabs ofindividual sections of each of the three linked sections engage the tabreceiving recesses of individual sections of the other laterallyadjacent linked sections so as to connect such individual sections andconnect the respective laterally adjacent linked sections as the linkedsections are extended.
 2. The method of claim 1, wherein the verticallyadjacent individual sections of each linked section pivot with respectto the other vertically adjacent individual sections about a pivot axisproximate the first end of the respective individual section, whereinthe pivot axis for each of the respective individual sections of eachlinked section are substantially parallel to one another.
 3. The methodof claim 1, including the step of rotating the power screw so as toraise vertically adjacent individual sections in each of the threelinked sections to extend the extendable/retractable tower.
 4. Themethod of claim 1, wherein each of the individual sections includes atleast one projection extending from the first side, and at least oneside opening proximate the second side for engaging such a projection;wherein at least one of the at least one projections of an individualsection of each of the three linked sections can engage with at leastone of the at least one side opening of a laterally adjacent individualsection of another of the three linked sections so as to distribute thevertical load along the individual sections when the individual sectionsare raised.
 5. The method of claim 1, wherein the drive mechanismincludes three power screws, each power screw having a spiral drive rib,wherein the drive openings of each of the respective individual sectionsof each of the three linked sections are spaced apart and oriented toaccommodate the dimensions the spiral drive rib of the respective powerscrew, the respective series of drive openings extending between thefirst end and the second end of each individual section; wherein thestep of rotating power screw includes rotating the spiral drive ribs ofeach of the three power screws when each of the spiral drive ribs areengaged with the drive openings of respective individual sections so asto raise the individual sections of each of the three linked sections.6. The method of claim 1, wherein the drive mechanism includes threepower nuts, each of the power nuts including a series of linked lugshaving lifting pegs; wherein the power screw includes a spiral driverib; and the series of drive openings includes a set of openings whichare spaced apart and oriented to accommodate the dimensions the liftingpegs, the set of openings extending between the first end and the secondend; wherein the step of rotating includes the step of engaging thespiral drive rib of the power screw with each of the three power nuts todrive the power nuts so as to engage the lifting pegs with the driveopenings to raise the individual sections of each of the three linkedsections.
 7. The method of claim 1, wherein each of the three linkedsections is initially rolled up in a bale; wherein the step of rotatingincludes the step of unrolling each of the bales as the power screw isrotated so as to raise the individual sections.
 8. The method of claim1, wherein the step of rotating the power screw in a first direction isfollowed by a step of rotating the power screw in a second directionthat is the opposite of the first direction to lower the individualsections and disengage the respective connection tabs and tab receivingrecesses to separate individual sections of each of the three linkedsections from individual sections of other of the three linked sections.9. The method of claim 8, wherein the step of rotating the power screwin the second direction includes rolling up the individual sections ofeach of the three linked sections to form a bale.
 10. The method ofclaim 1, wherein the power screw is oriented to have a vertical axis,and wherein the step of rotating the power screw includes rotating thepower screw about the vertical axis so as to extend the individualsections in a vertical direction.